The edge machining of workpieces made of wood or wood-like material such as chipboards, floor panels or the like is associated with a high degree of chip production. The chips have to be removed as promptly and completely as possible from the point of origin, that is, from where the tool cutting edges come into engagement with the workpiece edge, and carried away. Otherwise, they can have various disadvantageous effects, such as multiple chipping, development of heat, formation of impressions on the workpiece surface or the like.
Guide devices for guiding the workpiece along the circumferential contour of the rotary tool are provided in the prior art. Such guide devices comprise at least two pressure elements that are located opposite one another in a vertical direction, specifically an upper pressure element and a lower pressure element, between which the workpiece is held and guided. At least one of the two pressure elements is settable in the vertical direction relative to the respective other pressure element and also relative to the drive unit, in order that the desired edge profile arises at the right point on the workpiece.
Furthermore, use is made of chip collecting hoods which are fastened to the drive unit and cover the tool and the cutting region. A connected suction fan is intended to extract the chips in a controlled manner. A machine tool having such a chip collecting hood is known from U.S. Pat. No. 8,074,688. Therein, the edge of a workpiece is machined by upcut milling by means of a rotary tool. The rotary milling tool and also the edge region of the workpiece are enclosed virtually tightly by the chip collecting hood in order to ensure good extraction. In particular that region of the hood that immediately adjoins the workpiece edge is problematic. Not only does the chip collecting hood have to allow the workpiece to be guided up to the cutting region of the rotary tool, the hood also has to reach as close as possible to the workpiece surface in order to prevent chips escaping in an undesired manner there. For this purpose, the side wall of the chip collecting hood has a cutout which encloses the cross section of the workpiece edge with a slight gap.
In upcut operation, the chips removed from the workpiece are flung away at an oblique angle relative to the workpiece edge. A considerable proportion of the flung-away chips does not directly reach the abovementioned gap and can be extracted. However, it is not possible to prevent a certain proportion of chips from passing out undesirably through the gap. This problem is even more pronounced when the machine works in downcut operation. In this case, the removed chips are flung away substantially parallel to the workpiece edge immediately after they have been produced, with the consequence that they reach the gap more or less directly in a high concentration and can emerge there.
In practical operation, such machine tools have to be able to be operated universally and are therefore provided with different setting capabilities. Upon changing between workpieces of different thickness, the circumferential wall and the cutout formed therein also have to be adapted in the height or vertical direction in order to maintain as small as possible a vertical gap dimension between the workpiece surface and cutout edge. The same goes in a corresponding manner in the event of a correction of the spacing between the drive unit and workpiece edge. If, for example, the radius of the tool is reduced during sharpening, this is associated with a reduction in diameter, as a consequence of which the spacing dimension has to be corrected. Since the hood is fastened to the drive unit, the cutout is also displaced, together with the drive unit, relative to the workpiece edge. Consequently, complicated correction of the cutout in the hood wall is also necessary in the depth direction.